This invention relates to the widespread use of fuel canisters by campers and backpackers and their ability to utilize canisters they carry with them to also power an insect repellent device.
The assignee of the present invention is also the assignee in interest of prior patents relating to controlled fuel gas flow to heat a device for repelling insects and/or powering a portable heating appliance: U.S. Pat. No. 4,733,651; U.S. Pat. No. 4,759,343; U.S. Pat. No. 4,699,123; and U.S. Pat. No. 5,700,430. These prior art appliances contain a fuel supply cartridge which supplies fuel to burners which heat the appliance. The cartridge may contain propane or butane, and often contain a mixture of the two, under sufficient pressure to liquefy the gases. In order to compensate for variations in vapor pressure, which varies with fuel composition and temperature, these prior art devices use pressure regulators to help control gas flow.
During operation, when a cartridge containing the gas fuel is inserted into the appliance, the cartridge valve is not opened and fuel does not flow to the pressure regulator. When the appliance is turned on, the regulator pushes a plunger into the cartridge valve, opening it and allowing gas to flow. When a predetermined pressure is reached, the gas acts upon the diaphragm in the regulator to reduce or stop the gas flow by closing the cartridge valve. Thus, while the part of the regulator that senses pressure is in the appliance, the device that controls gas flow is in the valve built into the cartridge.
There are also numerous camping stoves in the prior art, for cooking and for heating, which rely on gas supplied by canisters but which do not have a pressure regulator. The gas flow in these devices is user-controlled via needle valves. Some stove models do have regulators, but they still have needle valves for user control of the gas flow.
Many campers, RV users, hunters and backpackers who enjoy the outdoors are subject to insect attacks for extended periods of time. The operating times of the insect repellent devices described in the above-listed patents are limited by the amount of fuel in their cartridges. There remains a need for longer term use of insect repellent devices powered by a portable fuel source. There remains also a need for devices that are self-regulating in their fuel flow rate, for reasons of safety and ease of operation.